A teletherapy radiation capsule composed of the following: A.) an international standard source holder (usually lead), B.) a retaining ring, and C.) a teletherapy “source” composed of D.) two nested stainless steel canisters welded to E.) two stainless steel lids surrounding F.) a protective internal shield (usually uranium metal or a tungsten alloy) and G.) a cylinder of radioactive source material, often but not always cobalt-60. In the Goiânia incident it was caesium-137. The diameter of the “source” is 30 mm.